Micrometer gauge



DecQZl, 1943. J w TODD 2,337,509

- I MICROMETER GAUGE Filed Dec. 50, 1941 2 Shets-Sheel: 1

15 3 1 '35 79 Q v :i v

' imm'oR" ATTORNEYS Dec. 21, 1943. .1. w. TODD MICROMETER GAUGE Filed Dec. 30, 1941 2 Sheets-Sheet \NVENT R MTMA f TT0R Patented Dec. 21, 1943 JUN! T E D STATE S r oer cs assnsoe MIcRoME'r R Ga ners John William Todd, Gity' Road,-London,

' England Application December 30, 1,941, .SerialNo. 424,975 In Great'Britain .Ianuary'Z, 1,941

6 Claims.

I This invention relates to micrometer gauges .or-comparators. and has for'its object to provide an improved gauge which'is particularly designed for the accurate. measurement of small holesand other apertures not easily measured byinstruments of .known type but which is also .capableof use for external measurement. According to the invention the improved micrometer gauge includes a pair of jaws adapted tobe insertedin the aperture or placed across thesurfaces to be measured, one of said jaws beingfcarried by a pivoted arni adapted to be adjusted by handto set the jaws and also to actuate an indicating device capable of showing any deviation from" a. predetermined measurer'ne'ntY w In order thatthe invention may be more fully understood'reference will now be made to the accompanying drawings which illustrate two embodiments of the invention and wherein- Fig. 1 shows the improved gauge in its sim-'" plest form.

Fig. 2 shows a modified form of gauge capable of measuring over a large range and Fig. 3 shows the method of assembling the gauge of Fig. 2 to adapt it for external measur- "Referringto Fig. 1, the improved micrometer gauge comprises a frame it one end H of which "is formed to constitute one of a pair of jaws'll,

12 which areaclapted to be set to a predetermined measurement and inserted in the aperture I 3 to be measured. The second jaw I2 is arranged to lie substantially parallel to the jaw II and is formed integral with a lever arm M which is pivotally mounted at l5 in a fork l6 formed on the upper end of a standard l1, said standard being mounted for vertical adjustment within an aperture or recess l8 formed in the frame l0 and being threaded to receive two knurled nuts I9 by which it is clamped in the desired position of adjustment.

The end of the frame l0 remote from the jaws is formed integral with a bracket or U- shapedv structure the limbs of which are bored as at 2| to provide sockets for a dial test india. may be providedfor clamping the dial test indicatorinthe bracket structure 29, for example, the end of the bracket could be slotted longitudinally and a clamping screw 25 provided,

...and similar or other means may also be provided for securing the bush 23 against displacement.

Preferably springmeans, for example a blade spring]? engaging. the lever arm M, is provided tourge the jaws apart to the limit determined by the setting of the screw 24 and, when the ,gaugeisto be used for measuring cylindrical "apertures, a spring blade 28 is providedwhich is formedat its sides with upwardly extending .arms orv lugs 28a adapted to engage the aperture ,wallon either side of the upper jaw I2, said spring device being used to keep the fixedj'aw l ljpres'sed against one side of the aperture wall tobe measured and. to centralize the jaws H, l2. The, device above described is set initially by inserting the jaws between the points of a standard gauge, micrometer or other device giving the ,required dimension and by adjusting the screw 24 and standard 57 until the arm M is vpositioned to set the jaws substantially parallel and at thedesired distance apart. When, thereafter, the jaws are inserted in a hole or other aperture any slight deviation below the pre-set measure- .ment will rock the lever arm M slightly and the stem. of the test indicator will be lifted whereby dial.

'. The gauge above described is of particular use an indication of the deviation is given on the in measuring small cylindrical apertures of the order of A; inch to inch internal diameter as the jaws can be inserted into the aperture to a sufficient extent to indicate whether it is truly cylindrical or slightly tapered. To ensure accuracy the outer or inner surface of each jaw may carry a ball-point or similar member for the purpose of making only point contact with the surface of the aperture to :be measured. In theipreferred arrangement the fixed jaw is pro- .vided with two-ball-points 29a, 291") along its length and the movable jaw with one ball point 2% disposed mid-way between the ball points on the'fixed jaw. This arrangement enables the maximum or minimum dimensions in one direction to be very easily located.

The form of the invention according to Fig. 2 differs from that shown in Fig. 1 in that the jaws I la, l2a are detachably mounted on the frame In and lever arm I4 thus rendering them interchangeable With jaws of diiferent size or form. The jaws may be mounted in any convenient manner but in the preferred form they are each and using a clamping screw 33 or in any other .suitable manner.

threaded directly in the bracket structure. Finally, it may be found more convenient to substitute for the spring 21 a coiled tension or compression spring extending between the lever arm and frame member or a coiled spring mounted on the lever arm pivot.

I claim:

1. A micrometer gauge or comparator comprising a frame member carrying a fixed jaw, a lever arm pivotally mounted on a standard adjustably supported on aid frame member and The jaws Ila, l2a. may be provided with m1 or other contact points as in the form previously described or, to enable the device to be used for, the measurment of different shaped apertures.

including internal screw threads both coreand effective diameters, internally recessed bores and the like, the outer ends of the jaws may carry detachable nibs 34 which make the actual contacts with the surfaces to be measured.

An additional socket 35 may be provided in the frame member to form an alternative mounting for the jaw Ila and thus extend the range of use of the instrument and, if desired, asimilar dual mounting may be provided on the lever arm I4 for the jaw l2a.

The other parts of the gauge are constructed and assembled as in the form shown in Fig. 1 with the exemption that'a modified form of blade spring 21 i used which can be easily reversed to ,bear upon the lever arm on the opposite side of the pivot for a purpose now to be described.

v carrying at one end a second jaw in substantially parallel relation with the fixed jaw, an adjust- 1 ing screw mounted in the frame member so as to bear against the other end of said lever arm and adapted to set the distance between the jaws to a predetermined measurement; a spring holding said lever arm in engagement with the adjusting screw and a. test indicator supported on an extension of the frame member in such manner as to be operated by said lever arm to indicate any deviation of the jaw from the set In Figs. 1 and 2 I have shown the improved -g-auge arranged for internal measurement but jbcth forms of the invention may be adapted for ,external measurement by reversing the operation ,of the lever arm, and Fig. .3 shows the instru- ;ment illustrated in Fig. 2 adapted in'this man- ;ner. It will be noted that the lever arm is inyerted and the positions of the test indicator 22 and adjusting screw 24 are interchangedforwhich purpose the bush 23 is mounted in the upper socket 2|.

In addition the spring blade 28 is removed, the spring 21 is reverved so that its action is to urg the movable jaw towards the fixed jaw, and the jaws or the detachable nibs, or both, are reversed so that the contact points face each other. The method of using the gauge in this form is similar to that prewlously described. The jaws having been set the desired distanceapart by manipulation of the screw '24 and nuts 19, they are placed across the external surfaces,'the distances between which is to be tested,in.the manner of calipers and any variation above the standard te which the instrument is set will spread the jaws, thus rocking the lever arm and recording the deviation on the indicator.

It will be understood that the devices illustrated are given by way of example only and that various modifications may be made without departing from the spirit of the invention particularly in the arrangement of interchangeable jaws and nibs. Wherethe instrument is to be used for internal or external work only, the .bush

23 may be dispensed with, the screw 24 being measurement.

2. A micrometer gauge or comparator comprising a frame member, a pair of jaws adapted to be inserted in the apertur or placed across the surfaces to be measured, one of said jaws being fixed and carried by the frame member, a lever arm carrying at on end the other jaw and having a pivotal support which is adjustable relative to the frame member, and hand operated means engaging the other end of said lever arm for setting the jaws to a. predetermined measurement,

' the said lever arm being adapted to actuate an indicating device for showing any deviation of the jaws from their present position.

, 3. A micrometer gauge or comparator according to claim 2, wherein said hand operated etting means consists of an adjusting screw mounted in said frame member.

4. A micrometer gauge or comparator accord- 7 ing to claim 2, wherein said lever arm is pivotally mounted on a standard having a screw-threaded stem which traverses an aperture formed in said frame member and has clamping nuts thereon for securing it in the adjusted position.

5. A micrometer gauge according to claim 2, wherein said hand operated setting means comprises an adjusting screw engageable with one side of said lever arm and said indicating device comprises a test indicator having a stem engageable with the other side of said lever arm, adjusting screw and test indicator being mounted interchangeably and said lever arm being mounted reversibly in said frame member whereby the gauge may be adapted for internal or external measurement.

6. A micrometer gauge according to claim 2, wherein two ball points are spaced along the length of said fixed jaw and one ball point is provided on the movable jaw and is spaced midway between the points on the fixed jaw for ensuring accurate engagement with the surfaces to b measured.

, JOHN WILLIAM TODD. 

